If you want to have back all the original ubuntu packets, you can try: sudo aptitude install ubuntu-desktop. Quoting from here:

ubuntu-desktop: In addition to ubuntu-base, this package depends on all of the packages in the Ubuntu desktop system. It installs a desktop environment (GNOME) and lots of software for home and office use.

That's surely the fastest way to restore ubuntu to its initial packet state.

If gnome-panel is not installed, install it using sudo apt-get install gnome-panel

And try gnome-panel again. It will show up.

In my case during installation I noticed that it is also installing evolution-data-server, gnome-applet, indicator-applet-appmenu, indicator-applet-complete and libedataserverui. From which, last day I had uninstalled evolution-data-server myself.